When it comes to eradicating infectious diseases, there can be no half measures: it’s an all-or-nothing proposition.
For more than three decades, eradicating polio — removing it from the face of the earth — has been the sole mission of the Global Polio Eradication Initiative (GPEI). But now, after helping drive down the global number of cases by 99.9%, and with the wild poliovirus only endemic in just two countries, this incredible initiative is in danger of becoming a victim of its own success. With so few cases reported around the world, compared to when its efforts first began in 1988, can the initiative persuade donor governments that polio eradication remains a global priority?
Until a few decades ago, nuclear annihilation was the only thing Americans feared more than polio. Wards of children encased in iron lungs emphasized the severity of the disease. But now, with cases confined to marginalized and deprived regions, donor governments may be less willing to bankroll GPEI’s new $4.8 billion five-year strategy on Oct. 18 during the World Health Summit in Berlin. With G20 governments still reeling from the economic impact of the Covid-19 pandemic and bracing themselves for a global recession, I and others worry they may have grown weary of supporting this long-term initiative and only partially fund it, assuming that GPEI will just have to go with plan B.
But there is no viable plan B.
To eradicate polio once and for all, GPEI needs to be fully funded. If that doesn’t happen, the world can expect a disastrous resurgence of cases.
You don’t have to look far for evidence of this. In July 2022, New York experienced its first case of paralytic polio since the 1990s. Then came evidence that the virus had been detected in wastewater in the state. Given the low rates of polio vaccination in the population where this occurred, New York State declared a public health emergency. It isn’t alone. London and Jerusalem have detected poliovirus in their wastewater.
With rapid vaccination campaigns, good access to clean water and sanitation, and strong underlying population immunity, these discoveries are unlikely to become major public health threats. But they are examples of just how easily polio can come back when people are not vaccinated, and one reason why polio has remained a public health emergency of international concern since 2014.
Until now, much of GPEI’s work has been to support massive vaccination campaigns in countries where polio was still endemic, in conjunction with routine immunization efforts and other measures to stop transmission. This approach has been extremely effective at vaccinating people against polio in parts of the world where historically it had been very low. The problem, however, is that the highest-risk areas where the virus continues to circulate are invariably the hardest to reach and require concerted efforts and resources. This is why the final phase of the eradication program has taken so much longer than anyone anticipated.
This is heightened by the fact that, with a commonly used oral polio vaccine that is based on a live but weakened version of the virus, there is a small risk that when vaccinated children shed the weakened virus, it can circulate over time in areas with low vaccination coverage and revert back into a form that can cause paralysis. The chances of this vaccine-derived polio occurring are remote, and high vaccination coverage further reduces this risk. But the odds increase when large numbers of people are vaccinated without achieving high enough coverage to stop transmission. This creates pockets of missed communities in which the virus is able to emerge and circulate, and where vaccine-derived poliovirus cases can start to appear.
The case in New York is an example of this, but there are now hundreds more around the world. With the injectable inactivated poliovirus vaccine, which is now included as part of routine childhood immunization, there is no risk of this kind of transmission. But while the inactivated poliovirus vaccine provides protection against paralytic polio, it doesn’t prevent transmission, so both types of vaccine remain necessary for achieving eradication.
Despite these endgame challenges, GPEI has been making good progress. In 2015, one of the three types of poliovirus was declared eradicated. A second one was eradicated in 2019, leaving only one type remaining. The following year, after three years of no cases of wild poliovirus being detected in Africa, that continent was classified as free from endemic wild poliovirus. That left it confined only to pockets of Afghanistan and Pakistan.
But with cases circulating in these countries, it was only a matter of time before the virus was reintroduced to areas where it had previously been eliminated, with cases detected in Malawi and Mozambique.
The pandemic has hit polio vaccination hard. With immunization campaigns suspended and a backslide in routine immunization, more than 80 million children were put at risk of polio in the first few months of the pandemic. Since then, there’s been an upsurge of cases of both wild and vaccine-derived polio, including in areas where it had previously been eliminated.
GPEI aims to reverse that trend and make up enough ground to stop the transmission of wild poliovirus globally by the end of 2023, so eradication can be declared in 2026. It’s not the first time such targets have been offered. But what’s different this time around is that, in addition to mass vaccination campaigns, the initiative’s new strategy will be intensely focused on finding targeted ways to reach missed communities and take advantage of opportunities to become more integrated with other essential services. In these communities, children are not just consistently missing out on protection from polio, they are also missing out on a whole range of other critical health interventions and other vaccines.
It makes a lot of sense to join forces with other government programs and organizations like Gavi, which I lead, that are also focusing efforts on reaching communities where children are still not receiving a single routine vaccine dose, so-called zero-dose communities. This, together with catch-up campaigns and the increased rollout out of a next generation oral poliovirus vaccine that reduces the likelihood of vaccine-derived polio, is what it will take to end all types of poliovirus transmission and pave the way to eradication.
Anything less than this and the world risks unravelling three decades of progress and the chance of eradicating polio once and for all.
Seth Berkley is CEO of Gavi, the Vaccine Alliance.